class_docstr: Initialise a XMLBIFWriter object.
  
  Parameters
  ----------
  model: BayesianNetwork Instance
      Model to write
  
  encoding: str (optional)
      Encoding for text data
  
  prettyprint: Bool(optional)
      Indentation in output XML if true
  
  Examples
  --------
  >>> from pgmpy.readwrite import XMLBIFWriter
  >>> from pgmpy.utils import get_example_model
  >>> model = get_example_model('asia')
  >>> writer = XMLBIFWriter(model)
  >>> writer.write_xmlbif('asia.xml')
  
  Reference
  ---------
  [1] https://www.cs.cmu.edu/afs/cs/user/fgcozman/www/Research/InterchangeFormat/
docstr: Return the XML as string.
docstr_tok: ["Return","the","XML","as","string","."]
code: def __str__(self):
      """
      Return the XML as string.
      """
      if self.prettyprint:
          self.indent(self.xml)
      f = BytesIO()
      et = etree.ElementTree(self.xml)
      et.write(f, encoding=self.encoding, xml_declaration=True)
      return f.getvalue().decode(self.encoding)
  
imports: import xml.etree.ElementTree
  from io import BytesIO
  from itertools import chain
  import numpy
  import pyparsing
  from pgmpy.factors.discrete import State, TabularCPD
  from pgmpy.models import BayesianNetwork
  from pgmpy.utils import compat_fns
label_desc: Use image node_id 2 for calling the XMLBIFWriter obj's underlying member method code with example usage: obj.__str__() and returns: f